Protonated water clusters and their black body radiation induced fragmentation

Protonated water clusters H+(H2O)n, n = 5, …, 65 and their perdeuterated analogues were produced in a discharge sour and stored in an electromagnetic ICR-ion trap under collision-free conditions. The rates of their fragmentation or ‘evaporation’ due to absorption of the 300 K black body background radiation exhibit an overall τ ∼ 1n dependence. Local deviations of some clusters (e.g. n = 21 or 55) from the overall trend are attributed to their higher stabilities. The fragmentation is modeled by extrapolating macroscopic water droplet evaporation to the microscopic clusters.